1. Field of the Invention
This invention relates to gas turbines of the type which are convertible for use with different fuels and more particularly to a primary zone air proportioner for controlling the richness of fuel supplied to such turbines in accordance with the requirements of the particular fuel used.
2. Description of the Prior Art
An important design criterion for gas turbine power plants is that the plant accept a variety of different fuels and continue to operate efficiently. This criterion is becoming increasingly important as the future availability of certain fuels or fuel types becomes uncertain. Thus, for example, if liquid hydrocarbon fuels become scarce and/or prohibitively expensive, a power plant, to continue to operate economically, must be convertible to, for example, oil gas fuel or coal gas fuel. However, the optimum ratio of air to fuel varies for various types of fuels. When the proper air to fuel ratio for a particular fuel is established, not only does such a gas turbine run more economically by not consuming a mixture richer in fuel than is necessary, but also undesirable emission products produced from the fuel consumed by the plant are reduced.
Various devices for controlling the air to fuel ratio in an engine provide diverting air, whether it be preheated or not, for mixing with the fuel prior to or during combustion. Examples of fuel and air mixing devices for gas turbines can be found in U.S. Pat. Nos. 2,760,336 and 3,002,346 although this listing is obviously far from exhaustive.